With the commentary on the 400 vs 350 TPI, I edited some info that was
published on the SCCA Solo2 (autocross) BSP (class B, street/prepared) list.
The car that this engine was in ran at the Dogwood Grand Prix this year
(fastest Solo2 event in the country and only one on city streets I know of).
It took second out of 100 cars entered; first was also a Corvette with a
later engine. . .didn't beat him by much though.
The SCCA SP class doesn't permit nonstock head/cam swaps. . .mostly just
tuning, balancing, etc. He put alot of time into the car but not parts
dollars so this could be considered an alternate approach to building a 350
TPI motor. This car as modified below was very fast but of course I don't
have hp numbers. I hope to follow this guy's example with many of his mods
And even with the mods listed, it also passes emissions tests. . .interesting.
I cut out all of the suspension mod stuff as irrelevant for the old trucks
but it was just as interesting to me!!!. . . .
66 Corvair Monza turbo
86 Silverado short bed
86 Corvette Indy convertible, SCCA BSP #32
I decided to take a conservative approach. I know the L98 has killer low
& midrange torque in stock form. So, I just balanced the 90 engine when I
built it. Then I did a bunch of die grinding on the intake and exhaust
manifolds just to clean it up so it would flow a little better.
Specifically, I rounded out any corners and rough areas and totally
ground down the "dams" behind the throttle body since I disabled the EGR
system. I also matched the upper plenum openings to the runners that go
down to the lower manifold. On the lower manifold, I just made sure the
air would make a smooth turn from the runners to the heads.
The exhaust manifolds had some really gross AIR tubes protruding into
them. So, I ground them down and smoothed up the welds in the collector
area. I also "knife edged" the collector cross piece and rounded the edge
of the cone shaped collector transition. I capped the AIR tube on the
upper end. I had the EGR tube welded up on the passenger side manifold.
I got an 84 front Y pipe and gutted catalytic converter (plugged the AIR
tube). Then bought a new 85 rear Y pipe and connected up my Borla
Stock 700R4 as per Solo II rules (rebuilt last year). However, they allow
any torque converter, so I bought an Art Carr 2400 stall lock-up
converter (thanks for the tip Ken Mitchell!). I have the 3.07 rear gears
so my theory is that with the stock intake and stock free-flowing exhaust
that the converter would put the motor right in it's sweet spot.
With only 650 miles on the motor the acceleration was VERY strong. It
corners very flat and is dead neutral handling. I can use the throttle to
set the car where-ever I want on the course.
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